Recent years have witnessed the growing popularity of digital cameras, which make use of image pickup elements such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor to convert an optical image into an electrical signal, and digitize and record this electrical signal. With such digital cameras, there is a need not only to increase the number of pixels of the CCD or CMOS sensor, but also to improve the performance of the lens barrel that forms the optical image on these image sensors. More specifically, there is a need for a lens barrel equipped with a high-power zoom lens system.
Meanwhile, the housing of a digital camera needs to be made more compact in order to make the camera more portable. Therefore, there is a need for a reduced size image pickup device equipped with a lens barrel and image pickup elements, which is believed to contribute greatly to reducing the size of the body. In these efforts to obtain a smaller image pickup device, what is known as a bending optical system has been proposed, in which the size of the device is reduced by bending the zoom lens system on its optical path, without changing the optical length.
For instance, Patent Document 1 discloses a bending optical system in which a reflecting mirror is used to bend the optical path. More specifically, the lens barrel disclosed in Patent Document 1 is equipped with a first lens group and a second lens group, in order from the subject side, on the subject side of the reflecting mirror, and is equipped with a third lens group and a fourth lens group, in order from the reflecting mirror side, on the image pickup element side of the reflecting mirror. The first lens group is fixed. The second lens group and third lens group are each capable of moving in the optical axis direction, and a zoom lens system is constituted by the joint movements of these lens groups. The fourth lens group is used for focal adjustment.
Also, Patent Document 2 discloses a bending optical system in which a prism is used to bend the optical path. More specifically, the lens barrel disclosed in Patent Document 2 is equipped with a lens group on the subject side of the prism. The lens group is capable of moving in the optical axial direction between a usage position and a stowed position. The prism is also capable of moving so as to ensure enough room for storage when the lens group is in the stowed position.
Patent Document 3 discloses a constitution of a lens group used in a bending optical system.
However, further improvement will be required before the need for a high-power zoom lens system and the need for a small size can both be achieved at the same time.
More specifically, with the constitutions disclosed in Patent Documents 1 and 2, it is difficult to obtain a high-power zoom lens system while at the same time reducing the size of the device. Furthermore, even if the lens configuration disclosed in Patent Document 3 is employed, no constitution for reducing the size of the device is disclosed, and the specific device constitution is unclear.
Meanwhile, when an image pickup device is reduced in size, or is equipped with a high-power zoom lens system, it is generally necessary to prevent blur of the captured image, the main cause of which is camera shake and so forth.
FIG. 33 is an exploded perspective view of an image blur correcting device in an example of prior art (see Patent Document 4). With the image blur correcting device shown in FIG. 33, a second lens group 101 is supported by a lens frame 102, and the lens support frame 102 is movably supported by a guide shaft 103 that guides movement in the pitch and yawing directions. Also, the lens frame 102 is provided with coils 104a and 104b for driving the lens frame 102 in the pitch and yawing directions. Magnets 106a and 106b are provided for a stationary base 105, opposite to the coils 104a and 104b, respectively. When power is applied to the coils 104a and 104b, drive force is generated in each direction, and the second lens group 101 is driven in the pitch and yaw directions. The amount of blur of the lens barrel is sensed by angular velocity sensors 107a and 107b, power is applied to the coils 104a and 104b according to the sensing signal, and image blur is corrected.
Patent Document 1: Japanese Laid-Open Patent Application H11-258678
Patent Document 2: Japanese Laid-Open Patent Application 2003-169236
Patent Document 3: Japanese Laid-Open Patent Application 2004-102089
Patent Document 4: Japanese Laid-Open Patent Application 2000-75338 (FIG. 4)